This application claims prior benefit from German application 100 06 396.9 filed on Feb. 12, 2000 and German application 199 21 010.1 filed on May 6, 1999.
1. Technical Field
The invention relates to a heating system, particularly for motor vehicles, in which a heat exchange arrangement operating in the manner of a heating member can be thermally coupled by means of a hydraulic heat transfer circuit, particularly a water circuit, to a first heat source, in particular an internal combustion motor serving to drive the motor vehicle, and also to a second heat source, in particular a burner operable independently of the first heat source, wherein a control arrangement can be changed over, in dependence on the operating state of a first pump allocated to the first heat source, between a first state, in which the heat transfer medium or at least a greater portion of it is conducted over both heat sources, and a second state, in which the heat transfer medium is conducted by a further, hydrodynamic pump, only or preponderantly over the second heat source.
2. Technology
Such heating systems are fundamentally known and are built into motor vehicles in mass production. The control device operates with valves or thermostats in order, in dependence on the operating conditions at any given time, either to switch over to the so-called large circuit, which includes both heat sources, or to the so-called small circuit, which leads only over the second heat source. If necessary, a mixed circuit can also be switched in, in which one part of the heat transfer medium is conducted over both heat sources and another part of the heat transfer medium is conducted solely over the second heat source. Reference is made in this regard to DE 43 24 371 A1 and to DE 44 46 152 A1.
The invention has as its object to simplify the control of the circuits.
This object is attained according to the invention in that the further pump has a radial impeller axially displaceable in a pump housing with radial forwarding vanes arranged on its one face and also a pump inlet arranged axially in front of this face and two radial pump outlets spaced apart from each other in the axial direction of the impeller, and that the pump outlet axially remote from the pump inlet communicates with the inlet side of the first heat source, and the pump outlet axially nearer to the pump inlet communicates with the inlet side of the second heat source.
The invention rests on the general concept of rendering superfluous the valves which were heretofore customary for the control of the heat transfer circuits, by means of a particular construction of the further pump, which in the invention is constituted as a multi-hydrofunction pump. The axially displaceable radial impeller assumes different positions relative to the radial pump outlets when only the first pump, or only the second pump, or both pumps, are operating, wherein in the last case the position of the radial impeller also depends on the delivery rates of the two pumps relative to each other. When only the further pump is operating, only a little heat transfer medium can flow out from the further pump to the first pump, independently of the axial position of the radial impeller. The preponderant fraction of the heat transfer medium flows out to the second heat source via the pump outlet axially nearer to the pump inlet. At the same time, there arises at the face of the radial impeller having the forwarding vanes a dynamic reduced pressure which xe2x80x9cpullsxe2x80x9d the radial impeller axially into a position adjacent to the pump outlet to the second heat source, in which position the radial impeller can particularly effectively maintain the small circuit.
When only the first pump is operating, the radial impeller is pushed into a position distanced from the pump inlet, with extensive release of the pump outlet leading to the first heat source.
When both pumps are operating, the radial impeller assumes a middle position which depends on the relationship of the pressures arising at the pump outlets and correspondingly on the relative delivery rates of the two pumps.
According to a first embodiment of the invention, the radial impeller can be arranged to be axially displaceable on a drive shaft.
Instead of this it is also possible to arrange the drive shaft to be axially displaceable together with the radial impeller, where if necessary an associated drive motor, as a rule an electric motor, can be displaced with the shaft.
As for the rest, the pump housing can enclose the radial impeller with more or less great radial play, so that the two pump outlets communicate with each other independently of the axial position of the radial impeller.
According to a particularly preferred embodiment, the radial impeller or a portion thereof can have a shape which can change in dependence on temperature, so that at higher temperatures of the heat transfer medium a bypass is always provided between the inner space of the pump housing on the front side and the inner space of the pump housing on the back side. The variable shape can be attained by shape memory alloys, as described hereinafter.
According to a further preferred embodiment, the radial impeller can cooperate with a stop which changes its shape or position in dependence on temperature, this stop, below a transition temperature or a lower temperature threshold value, permitting an axial displacement of the radial impeller by flow-dynamic forces between two end positions, in which the radial impeller supplies the heat transfer medium either preponderantly to the one radial pump outlet, or preponderantly to the other radial pump outlet, and wherein the stop, above the transition temperature or an upper temperature threshold value, brings the radial impeller into such an axial position, or restricts the axial mobility of the radial impeller in such a manner, that at least a partial stream of the heat transfer medium flows into the radial pump outlet more distant from the pump inlet.
Such a temperature-dependent change of the axial displacement path of the radial impeller can take place by means of bimetal springs orxe2x80x94in a particularly appropriate mannerxe2x80x94by a spring made of shape memory alloy.